1. Technical Field
An improved hypotube for an intravascular catheter is disclosed. More specifically, an improved hypotube for use with a catheter is disclosed that provides improved strain relief or transitioning stiffness characteristics between a distal end of the hypotube and a proximal end of the catheter.
2. Description of the Related Art
Intravascular catheters are widely used for a variety of diagnostic and therapeutic purposes. Specifically, angioplasty has been developed as an alternative to bypass surgery for treating vascular diseases or other conditions that occlude or reduce blood flow in a patient's vascular system. Balloon angioplasty has proven to be a useful and often a preferred treatment for coronary diseases that cause blockages, also known as stenosis, in coronary arteries as well as other parts of the vascular system.
One current angioplasty technique makes use of a single operator exchange or rapid exchange catheter assembly as illustrated in U.S. Pat. No. 5,156,594. The catheter assembly shown therein includes a balloon catheter having a proximal end including a hypotube. A distal end of the balloon catheter is connected to a balloon. The balloon catheter includes a main lumen that is in communication with the lumen of the hypotube as well as a relatively short separate lumen which accommodates a guidewire. In practice, the guidewire is inserted into the patient's vascular system through a guide catheter. The balloon catheter assembly is then fed through the guide catheter and over the guidewire. The guidewire is fed through the distal end of the guidewire lumen and out the proximal end of the guidewire lumen which is disposed proximal of the balloon. In contrast to an over-the-wire catheter system, if the catheter needs to be changed, the position of the guidewire can be maintained by withdrawing the catheter without the need for a long guidewire or an extension wire.
Advancing the catheter assembly to position the balloon across a stenosis can be a difficult and time consuming task due to the narrow and tortuous passages through which the catheter assembly must be passed. The balloon must be positioned precisely and movement of the balloon through the vascular system must be conducted in as atraumatic manner as possible.
To be effective, the catheter assembly preferably has two distinct features. First, the catheter assembly must have sufficient “pushability” or axial strength thereby enabling a longitudinal force to be transmitted through the assembly so that the physician can push the catheter assembly through the vascular system to the stenosis. Concurrently, the catheter assembly preferably may also be sufficiently flexible so that the catheter assembly has good “trackability” so as to enable the physician to navigate the tortuous passages of the patient's vascular system.
To satisfy these criteria, balloon catheter assemblies typically have a stiff proximal end and a more flexible distal end. If a hypotube is used at the proximal section, it is typically manufactured from a metallic material, such as stainless steel. The balloon catheter or the distal section of the assembly is typically manufactured from a more flexible, polymer product. Thus, the hypotube is relatively stiff, enabling the assembly to have good pushability while the balloon catheter or tube is more flexible, enabling the assembly to have sufficient trackability.
One problem associated with connecting a relatively stiff tubular member, such as a hypotube, to a more flexible tubular member, such as the catheter, is that the transition between the stiff hypotube and the more flexible catheter can result in kinking which can close the lumen of the hypotube or the lumen of the catheter thereby blocking flow through these lumens to the balloon.
To solve this problem, stiffening members have been provided which help serve as a transition member between the hypotube and the catheter. Such stiffening members are disclosed in U.S. Pat. Nos. 5,658,251 and 6,066,114.
As angioplasty and stent delivery procedures continue to increase, there is a continuing need to provide new catheter systems and improved trackability and flexibility.